Download or read book Development and Application of Optical Dating Using Quartz and Potassium-Feldspar from Quaternary Sediments written by Bo Li, (Wr and published by Open Dissertation Press. This book was released on 2017-01-27 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: This dissertation, "Development and Application of Optical Dating Using Quartz and Potassium-feldspar From Quaternary Sediments" by Bo, Li, 李波, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: Abstract of thesis entitled DEVELOPMENT AND APPLICATION OF OPTICAL DATING USING QUARTZ AND POTASSIUM-FELDSPAR FROM QUATERNARY SEDIMENTS Submitted by Bo Li for the Degree of Doctor of Philosophy at The University of Hong Kong in November 2007 New methods were presented for the dating of Quaternary sediments using luminescence signals from quartz and potassium-feldspar (K-feldspar) grains. These are based on fundamental studies carried out on separated quartz and feldspar grains. Estimation of the equivalent dose using the fast component and the medium component of optically stimulated luminescence (OSL) from quartz grains was investigated using both linear-modulated OSL (LM-OSL) and continuous-wave OSL (CW-OSL) techniques. By mathematical fitting of the LM-OSL curves, the fast component of the quartz OSL signal can be separated from the signals observed for mixed mineral grains in order to determine the equivalent dose (D ). The medium component underestimates the D for old samples, and this is attributed to its thermal e instability. A method was proposed to evaluate the D values for the fast component and medium component by analyzing the D as a function of stimulation time. Three kinds of source traps (i.e. shallow, medium and deep sources) for thermal transfer in quartz were identified. The shallow source is thermally unstable below 260C and is mainly related to the main OSL trap. The medium source is the primary charge source (peak 300C). The deep source is dominant at higher temperatures. Two kinds of OSL traps were identified as accepting the charges from the medium and deep sources. These OSL traps have different thermal stabilities and associated sensitization processes from those of the main OSL traps. A method was proposed to correct for thermal transfer effects for young samples based on the linear relationship between the initial and final parts of the thermally transferred OSL signals in repeated heat/OSL measurement cycles. A new isochron method involving measurement of the IRSL signals from K-feldspar grains of different size was proposed. It is based on the observation that the IRSL signal due to the internal dose does not appear to fade. The consistency between the isochron ages and quartz ages for 12 sediment samples from different geological settings suggests that the isochron method can be used to overcome anomalous fading. It can also be used to avoid problematic effects from changes in environmental dose rate. It was successfully applied to a lacustrine section showing significant changes in environmental dose rate due to a recent uptake of radioisotopes. The validity of the method was also tested using single grain IRSL measurements on K-feldspar grains. Optical dating using quartz was applied to the Holocene lacustrine and fluvial sediments at the Dagouwan section in the Sala Us River bank, Mu Us Desert. The results indicate that the Holocene Optimum occurred between 8.3 and 5.0 ka ago. After 5.0 ka ago, the Holocene Optimum terminated and the climate became dry again. The Sala Us River began to cut through the underlying Quaternary sediments after 2 ka ago with a down-cutting rate of 3-4 cm/year. The drainage of the Sala Us River accelerated the disappearance of the lake water and the deterioration of the local environment. However, impacts from human activities a